This article analyses how young people enrolled in drug addiction treatment in Copenhagen, Denmark, explain their cannabis careers and how they view their possibilities for quitting drug use again. Inspired by Mead and narrative studies of health and illness, the article identifies four different drug use ‘aetiologies’ drawn upon by the interviewees. These cover childhood experiences, self-medication, the influence of friends and cannabis use as a specific lifestyle. A central argument of the article is that these explanations not only concern the past but also point towards the future by assigning the interviewee a more or less agential position in relation to drugs. Further, the drug narratives are viewed as interactional achievements, related to the social context in which they were produced, namely, the institutional setting of the treatment centres. The article is based on 30 qualitative interviews with young people in drug addiction treatment.